Hi Peter, installing the front leaf springs might pull the subframe into proper alignment. Its worth a try and you have to do it sooner or later. I believe the leaf springs are part of the front end alignment, caster adjustment I think, so when you install them, you want them in the centered position as much as possible so there is room to make the alignment adjustments. You may have to search caster adjustment or similar to get more expertise than I can provide.
If it were me, attaching the leaf springs would be my next move. I assume the lateral rod is what I call the sway bar and I am not sure if attaching that would help your situation, again maybe someone with more expertise can weigh in.
Good luck.
Lee